The first means to disconnect service to the home, after the drop or lateral, is the service disconnect. The second panel may have been marked “main” which is exactly why we should know the correct terminology.

In cases where there is no single service disconnect, all (six or less) breakers would be considered part(s) of the service disconnect.

The service disconnect is always located within the service equipment.

Excellent points - It was wired as a sub (see pic) but still had a 200 amp disconnect. There was also a second sub that had been improperly wired - grounding conductors twisted together and not bonded to the panel.